From b428136eb53d2b1d3e8867ee7263f6a672320907 Mon Sep 17 00:00:00 2001
From: Taylor R Campbell <campbell@mumble.net>
Date: Thu, 5 Jul 2012 00:57:00 +0000
Subject: [PATCH] Try harder to mmap heap space.

Using mmap rather than malloc is important because we need read,
write, and execute privileges for the pages.

Some day, maybe we can change that requirement, but that day will not
be for a while.
---
 src/microcode/ux.c | 57 ++++++++++++++++++++++------------------------
 1 file changed, 27 insertions(+), 30 deletions(-)

diff --git a/src/microcode/ux.c b/src/microcode/ux.c
index 3a44513ab..2c818aa2e 100644
--- a/src/microcode/ux.c
+++ b/src/microcode/ux.c
@@ -743,52 +743,49 @@ mmap_heap_malloc (unsigned long requested_length)
       munmap (result, request);
     }
 
+  /* XXX We need to make the pages executable for native-code systems.  */
   return (OS_malloc (requested_length));
 }
 
+static void *
+mmap_heap_malloc_try (unsigned long address, unsigned long request, int flags)
+{
+  void * addr
+    = (mmap (((void *) address),
+	     request,
+	     (PROT_EXEC | PROT_READ | PROT_WRITE),
+	     (MAP_PRIVATE | MAP_ANONYMOUS | flags),
+	     (-1),
+	     0));
+  return ((addr == MAP_FAILED) ? 0 : addr);
+}
+
 #ifndef __linux__
 
 /* Try to use our low addresses even if the OS has a tendency to choose
    high ones.  (What if we're on a 64-bit system?  Why do we care?)  */
 
-#  ifndef MAP_TRYFIXED
-#    define MAP_TRYFIXED 0
-#  endif
-
 static void *
 mmap_heap_malloc_search (unsigned long request,
                          unsigned long min_result,
                          unsigned long max_result)
 {
-  void * addr
-    = (mmap (((void *) min_result),
-             request,
-             (PROT_EXEC | PROT_READ | PROT_WRITE),
-             (MAP_PRIVATE | MAP_ANONYMOUS | MAP_TRYFIXED),
-             (-1),
-             0));
-  return ((addr == MAP_FAILED) ? 0 : addr);
+  (void)max_result;             /* ignore */
+
+#ifdef MAP_TRYFIXED
+  {
+    void * addr = (mmap_heap_malloc_try (min_result, request, MAP_TRYFIXED));
+    return (addr ? addr : (mmap_heap_malloc_try (0, request, 0)));
+  }
+#else
+  return (mmap_heap_malloc_try (min_result, request, 0));
+#endif
 }
 
 #else /* defined (__linux__) */
 
 /* Use /proc/self/maps to find the lowest available space.  */
 
-static void *
-mmap_heap_malloc_try (unsigned long address, unsigned long request, int fixedp)
-{
-  /* MAP_FIXED clobbers any existing mappings, so fixedp may be true
-     only if the caller has already verified that there are none.  */
-  void * addr
-    = (mmap (((void *) address),
-	     request,
-	     (PROT_EXEC | PROT_READ | PROT_WRITE),
-	     (MAP_PRIVATE | MAP_ANONYMOUS | (fixedp ? MAP_FIXED : 0)),
-	     (-1),
-	     0));
-  return ((addr == MAP_FAILED) ? 0 : addr);
-}
-
 static int
 discard_line (FILE * s)
 {
@@ -846,15 +843,15 @@ mmap_heap_malloc_search (unsigned long request,
       if ((start + request) <= end)
         {
           fclose (s);
-          /* The space is known to be free, so we can request it fixed.  */
-          return (mmap_heap_malloc_try (start, request, true));
+          /* The space is known free, so we can safely request it fixed.  */
+          return (mmap_heap_malloc_try (start, request, MAP_FIXED));
         }
       start = next_start;
     }
 
   fclose (s);
  no_address:
-  return (mmap_heap_malloc_try (min_result, request, false));
+  return (mmap_heap_malloc_try (min_result, request, 0));
 }
 
 #endif
-- 
2.25.1